Let f(x)= 2x+2+1622x+1+2x+4+32. Then the value of 8 (f ( 115 )+f ( 215 )+ +f ( 5915 ) ) is equal to
- 108
- 92
- 118
- 102
Answer
(3) 118
Solution
f(x)= 4(2x+4)2(2x+4)2= 22x+4
f(x)+f(4-x)= 12
[figure]
k15 and 60-k15 pair up: 29 pairs + middle term f(2)= 14
Sum = 292+ 14= 594 8 594=118
Answer: (3)